Refrigerating apparatus



Feb. 3, 1959 E.- w. zEARFoss, JR 2,871,680

REFRIGERATING APPARATUS Filed July'lz, 1955 2 sheets-sheet 1 FIG.!

INVENTOR.

ELMER ZEARFOSS Jr.

ATTQRNEY FIG.

Feb. 3, v1959 Filed July l2, 1955 'E.-w. ZEARFOSS, JR

, REFRIGERATING APPARATUS 2 Sheets-Sheet 2 INVENTOR.

ELMER W. ZEARFOSS Jr.

ATTORNEY f asemis Patented Feb. 3, 1959 ice The present inventionrelates to a refrigerating apparatus of the type in which a capillarytube is employed to control the llow of refrigerant from the highpressure side to the low pressure side of the apparatus.

One object of the invention is to produce an improved refrigeratingapparatus of the type set forth.

When capillary tubes are employed as stated above, the evaporatorcircuit must be designed to keep liquid refrigerant from flooding orspilling into the suction line. Conventional llooded type of evaporatorconstruction incorporates refrigerant storage capacity such as tosuffice for maximum load requirements while obviating the spillageproblem. The practicable configurations of the circuit arel limited,however, and a relatively large quantity of ,refrigerant is required. Inthe dry expansion or series type of circuit an accumulator is employedat the outlet of the evaporator to trap excess liquid. This expedientresults in undesirable peak load and onset cycle performance whichreects improper refrigerant distribution and flow control. Furthermorethe inclusion of an accumulator creates oil logging problems.

A further object of the present invention is to produce a system whereinall of the foregoing problems are overcome.

More specifically, the object of the invention is to produce a whollyself-regulating refrigerating apparatus in which the amount ofrefrigerant distributed to the evaporator is automatically controlled bythe demand imposed on the evaporator to the end that the evaporatorwill, at all times, receive asupply of refrigerant which is a functionof the refrigerant leaving the evaporator.

A still further object is to produce an improved refrigerating apparatusin which flow control of the refrigerant reaching the evaporator iseffected without any moving parts and in a manner which does notappreciably increase the manufacturing cost of the apparatus and whichlinvolves no maintenance cost whatever.

In most types of apparatus involving use of a capillary tube it isnecessary that the refrigerant charge introduced into the sealed circuitbe accurately or, at least, very closely estimated. Otherwise, for wellknown reasons, satisfactory and eflicient operation may becomeimpossible.

It is therefore a kstill further object of the invention to produce animproved refrigerating apparatus in which the quantity of refrigerantintroduced into the system is not so critical and need not be accuratelypredetermined.

In all refrigerating machines, over-rides or extremes of evaporatortemperature, be they on the cold or on the warm side are not desirable.In other words, the cycling of the apparatus should be such as uniformlyto maintain the desired temperature range or limits.

It is therefore a still further object of the invention to produce animproved refrigerating apparatus which has cycling performance withoutundue over-ride.

These and other objects are attained by my invention as set forth in thefollowingspecification and as shown in the accompanying drawings inwhich:

Figure l is a diagrammatic representation of a refrigerating apparatusembodying my invention.

Figure la is a fragmentary and diagrammatic view showing slightmodifications which can be made in the apparatus shown in Figure 1.

Fig. 2 is similar to Fig. l, but showing a second embodiment of theinvention.

The embodiment of Fig. 1

When a refrigerating cycle begins, compressor 1 delivers compressedgaseous refrigerant to condenser 2 in which the gas is liquefied anddelivered to capillary tube 3 which leads to an accumulator 5, eitherdirectly, or

through nonrestrictive tube 4. In either case, a mixture of liquid andgaseous refrigerant is delivered to the accumulator. A restrictor 6leads from the bottom of the accumulator and a restrictor 7 leads fromthe top of the accumulator and, as can be seen from Fig. l, both ofthese restrictors lead to the inlet end of an evaporator 8. It will benoted that at this point in the refrigerating cycle, and with arelatively large pressure drop across restrictors 6 and 7, the flowcapacity of restrictor 6 will be sufficient to allow the passage of allof the liquid refrigerant which is delivered to the accumulator, as wellas some of the ash gas so that tube 7 need only accommodate theremaining flash gas. The flow of liquid refrigerant through theevaporator, refrigerates the latter, and its surrounding, and, as thefrost point progressively advances, liquid refrigerant will flow throughdischarge pipe 9 which is coiled around, or otherwise brought into heatexchange relation as at l@ with the accumulator. At this point in thecycle, the accumulator contains refrigerant gas only and because of thepressure drop across restrictors 6 and 7, the temperature of theaccumulator and its contents, is higher than the temperature of pipe 9.Therefore heat will flow via heat exchange l@ from the accumulator topipe 9. This heat transfer condenses the refrigerant gas in theaccumulator, and since the evaporator pressure is not alected by theheat exchange between the accumulator and pipe 9, the condensation ofrefrigerant gas reduces` the pressure within the accumulator andcorrespondingly decreases the pressure drop across restrictors 6 and 7.With the pressure in the accumulator thus reduced, liquid refrigerantwill not ow out through restrictor 6 at the rate at which it isdelivered to the accumulator through capillary tube 3, and thereforeliquid refrigerant collects in the accumulator and submerges the lowerend, or mouth, of restrictor 6. The diminished flow of liquidrefrigerant to the evaporator is reliected by the absence of liquidrefrigerant in pipe 9. In the absence of liquid refrigerant in pipe 9,the condensation of refrigerant gas in the accumulator ceases and thenow increased pressure within the accumulator will again increase liquidrefrigerant to ow, through restrictor 6, to the evaporator until liquidrefrigerant again reaches pipe 9 to begin a new cycle.

I have only described the extremes of the cycle, but it will beunderstood that in practice, moderate variations in the flow of liquidrefrigerant at heat exchange 1li of pipe 9, will regulate the ilow ofliquid refrigerant through restrictor 6. This between extremesmodulation of the cycle is especially effective when the load demand onthe evaporator is substantially constant. v

It is thus clear that, for best results restrictors 6 and 7 should be soproportioned that heat exchange effects aside, restrictor 6 will allowadequate flow of liquid ref frigerantto the -evaporator and that thecombined impedance of restrictor 6 and 7 shall besuch that the heattransfer potential of heat exchange 10 will be adequate to cause theflash gas component in the accumulator to be reduced to a value wherebythe reduced ow of liquid refrigerant through restrictor 6 will result inthe accumulation of liquid refrigerant in accumulator 5. It follows fromthe foregoing that the amount of liquid refrigerant in the accumulator,at any given time, will be a function of the load demand on theevaporator, so that the higher the load demand, the lower the level ofliquid in the accumulator, and vice versa.

In designs where load demands are high, heat exchange is also effectedby bringing pipe 9 into heat exchange with non-restrictive tube l at ll.In this arrangement, heat exchange 1l supplements the heat exchange atlo. It is also possible to omit the heat exchange at l@ and to use theheat exchange at Il alone. Under still other conditions, it is possibleto omit the heat exchange at Il) and the heat exchange at Trl. In thisarrangement, the heat exchange at l2 is employed and will exercise solecontrol of the system as follows: When liquid refrigerant in pipe 9, isbrought into heat exchange with capillary 3 at l2, the generation offlash gas is reduced, so that less gaseous refrigerant reaches theaccumulator, The reduction of gas pressure in the accumulator decreasesthe pressure drop'across restrictors 6 and 7 and correspondingly reducesthe ow of liquid refrigerant, through restrictor 6 to the evaporator. Asa result, only superheated gas will iiow in heat exchange with capillary3, at l2, and therefore the amount of gaseous refrigerant delivered tothe accumulator by capillary 3 will be greatly increased. The resultantincrease in the pressure drop across restrictors 6 and 7 will increasethe flow of liquid refrigerant from the accumulator to the evaporator,and so on. If it is desired to operate the system under substantiallythe exclusive control of heat exchange l2, the accumulator should beadequately insulated as, otherwise, changes in ambient temperature willaffect the pressure-temperature potential across theaccumulator-evaporator circuit.

I am aware that in conventional systems a heat exchange similar to heatexchange l2 has been used, but in these arrangements, the heat exchangereferred to only served to improve the eliiciency and to prevent liquidrefrigerant from reaching the compressor. As far as I am aware, I am thefirst to interpose an accumulator between the capillary and the inlet ofthe evaporator and to use heat exchange l2 as a thermal controlmechanism for the iow of refrigerant from the accumulator to theevaporator by modulation of the flash gas developed in the capillary inresponse to the state of the refrigerant in the suction line. In fact,in its broadest aspect, my invention may be said to consist ofaccumulator 5, restrictors 6 and 7 and heat exchange l2 because theseparts, alone will insure satisfactory operation for most purposes. Inother words, the heat exchange at lll, or the heat exchange at ll, needbe added when more refined control of the system is indicated.

The embodiment of Fig. 1A

In this embodiment, restrictors 6 and 7 of Fig. l are replaced byrestrictive openings l and 16 which are formed near the bottom and nearthe top, respectively, of a nonrestrictive tube 1d disposed withinaccumulator 5 which corresponds to accumulator S. In this embodiment,liquid refrigerant, flows into tube ld through lower hole I5 and gaseousrefrigerant will flow into tube E4 through upper hole 16.

In cases where practical considerations limit the size and, hence, therestrictive value of openings l5 and 16, an auxiliary restrictor 17 canbe provided between tube 14 and the evaporator, to supplement therestrictive action of holes l5 and f6. Preferably, the restrictive yalueof holes 15 and i6 themselves should be suicient to overcome the maximumhydrostatic effects which could be encountered during the operation ofthe system, to the end that the control of the system may not bematerially affected by the variable level of liquid refrigerant in theaccumulator.

The parts of this embodiment which have not been specifically describedand which are also found in the embodiment of Fig. l have beendesignated by the prime of the numerals of Fig. l. in this embodimenttoo, heat exchange 1l may be used alone, or as supplement to heatexchange 10 and both of these heat exchanges may be omitted whereby thesystem will be operated subject to the control of heat exchange 12 onlyin the manner set forth in connection with the embodiment of Fig. l.

The embodiment of Fig. 2

In this embodiment the 'accumulator is disposed hori- Zontally tominimize hydrostatic effects and a riser i9 extends upwardly from thetop of the accumulator. Extending within riser 19 is a tube 21, thelower open end of which is near the bottom of the accumulator and theupper portion of which is provided with a restrictive hole 22. Tube 2lleads through restrictor 23, to the inlet end of the evaporator. Exceptfor parts 19, 2l, 22 and 23, the remaining parts are the same as thoseof the embodiment of Fig. l and therefore have been designated by thesame numeral with the addition of the letter n to each of said numerals.

It will be apparent from inspection of Fig. 2 that hydrostatic factorsare essential to the operation and control of the system. Thus, at thebeginning of the refrigeration cycle, the pressure differential betweenaccumulator 5a and the inside of tube 2l by virtue of holes 22, is suchas to cause liquid refrigerant to flow lthrough tube 2l. When liquidrefrigerant flows through heat exchange lfcz, the gas in accumulator Eais condensed and the pressure drop across hole 22 is reduced,correspondingly to reduce the llow of liquid refrigerant through tube2l. The resultant starvation of the evaporator causes superheated gas toow through heat exchange 10a to increase the pressure differentialacross hole 22, whereby flow of liquid refrigerant to the evaporatorincreases and so on. From the foregoing it will be seen that therestrictive action of hole 22 must be correlated to thehydrostaticpressure of the liquid column in tube 21 or vice versa. Restrictor 23increases the pressure and temperature differential between accumulator5a and evaporator 8a in the same manner as restrictor 17 does in theembodiment of Fig. la. Since the restrictive action of tube 23'has adynamic effect, this must be taken into consideration in proportioningrestrictive passageway or hole 22, and the height of the column ofliquid in tube 21.

In this embodiment too, heat exchanges lla and 12a may be treated as theequivalents of their counterparts in Figs. 1 and la.

What I claim is:

l. In a refrigerating system including a compressor, a condenser, acapillary, a rst conduit, an accumulator, a rst restrictor, anevaporator, and a second conduit in a series flow path for refrigerant,said first restrictor leading from the bottom of said accumulator,asecond restrictor leading from the 'topy of said accumulator toward theinlet of said evaporator, and a heat exchange between said first andsaid second conduits whereby said heat exchange effects cooling of saidfirst conduit to modulate refrigerant pressure in said accumulator andcorrespondingly control flow of refrigerant to said evaporator.

2. In a refrigerating system including a compressorcondenser unit, afirst conduit, an evaporator, and a second conduit in a series ilowcircuit, flow control means comprising; an accumulator, two restrictiveoutiow passages from said accumulator, said one of said passages leadingfrom the upper portion thereof and said second of said passages leadingfrom the lower portion thereof, said accumulator and said passages beinginterposed between the outlet of said first conduit and the inlet ofsaid evaporator, and a heat exchange relation between portionsofsaidfirst andy said second conduits, whereby said heat exchangeeffects cooling of refrigerant flowing in said rst conduit to modulaterefrigerant pressure in said accumulator and correspondingly to controlflow of refrigerant to said evaporator.

3. The structure recited in claim 2 and further characterized in thatsaid first conduit includes a capillary tube.

4. The structure recited in claim 2 and further characterized in thatsaid restrictive passages are dened by measured openings formed in atube disposed within said accumulator7 said tube leading to the inlet ofsaid evaporator.

5. The structure recited in claim 4 and further characterized in that arestrictor is interposed between said tube and said evaporator inlet.

6. In a refrigerating system including a compressor condenser unit, anevaporator and a suction line for refrigerant flowing from saidevaporator to said unit, ilow control elements comprising; meansdefining a passage for refrigerant flowing from the outlet of said unitto the inlet of said evaporator, said passage including a capillarytube, a conduit, an accumulator, and a first restrictor disposed inseries ow relationship, said first restrictor leading from the bottom ofsaid accumulator, a second restrictor adapted for the ow of refrigerantfrom the top of said accumulator toward the inlet of said evaporator,and a heat exchange between a portion of said suction line and a portionof said passage, said portion of said passage being upstream of saidrestrictors, whereby said heat exchange effects cooling of refrigerantflowing in said passage to modulate refrigerant pressure in saidaccumulator and correspondingly control ow of refrigerant to saidevaporator.

7. Refrigerating apparatus of the kind including a compressor and acondenser for supplying refrigerant to a capillary tube, an evaporatorand a suction conduit for delivering gaseous refrigerant from saidevaporator to said compressor, ow control means comprising; anaccumulator disposed to receive a mixture of refrigerant from saidcapillary, a spaced pair of restrictive outflow ports defining passagefor liquid and gaseous refrigerant from said accumulator to saidevaporator, and a heat exchange between portions of said suction conduitan said accumulator.

8. In a refrigerating apparatus of the type which includes acompressor-condenser unit, 4au evaporator, and a suction line betweensaid evaporator and said unit, ow control means for modulating the ow ofrefrigerant towards said evaporator according to temperature changes insaid suction line, said flow control means being defined by a passagewayhaving a portion thereof in heat exchange with said suction line, saidpassageway connecting said unit and said evaporator and including acapillary tube, an accumulator, and two restrictive elements portingspaced regions of said accumulator to said evaporator, and said portionof said passageway being upstream of said restrictive elements.

9. The structure recited in claim 8 and a conduit interposed betweensaid capillary tube and said accumulator.

l0. In a refrigerating system, a flow control combination comprising; a-compressor-condenser unit, a passageway leading from said unit, saidpassageway including a capillary tube and an accumulator, an evaporator,a suction line between said evaporator and said unit, and tworestrictive elements adapted to connect spaced regions of saidaccumulator with said evaporator, said suction line being in heatexchange with a portion of said passageway; whereby the temperature ofsaid suction line on said passageway modulates the flow of refrigeranttoward said evaporator.

References Cited in the le of this patent UNITED STATES PATENTS2,459,173 McCloy Ian. 18, 1949 2,520,045 McGrath Aug. 22, 1950 2,685,780Zearfoss Aug. l0, 1954 2,697,331 Zearfoss Dec. 21, 1954 2,719,407Zearfoss Oct. 4, 1955

